As a storage controller, an apparatus that dynamically assigns partial areas of a pool area as data storage areas is known. A pool area is a physical storage area based on one or more RAID (Redundant Array of Independent Disks) groups, for example, which is an aggregate of one or a plurality of logical volumes, for example. A RAID group is configured by a plurality of physical storage devices, and a RAID group stores data at a predetermined RAID level. In the following description, the aforementioned physical storage area is called a ‘pool area’.
There are several types of functions that use a pool area.
A first type of function is a dynamic capacity extension, for example. More specifically, in cases where a data storage area is actually required, such as when a write operation from a host to a logical volume (virtual volume) supplied to a host apparatus takes place, for example, a partial area of a pool area is assigned as a data storage area.
Furthermore, a second type of function is snapshot management, for example. In specific terms, an image of a logical volume at a certain time point, for example, is stored, and an area for storing data (differential data) corresponding to a difference between a stored image and a current image is dynamically assigned from the pool area.
In Patent Literature (PTL) 1, a method for improving the usage efficiency of a storage area by allowing a plurality of functions to share a centrally managed pool area is described.